. >> reporter: hours earlier, he was officially sworn into office by chief justice john roberts at the white house. >> i barack hussein obama who solemnly swear. >> reporter: the constitution requires the both be delivered before noon on the 20th. vice president joe biden was also sworn in and together they laid a wreath at the tomb of ton known soldier. it's been a weekend full of events all leading up to the ceremony at the capitol. >> we're really excited. >> reporter: 800,000 people are expected to pack the national mall and security is tight. more than 13,000 military and law enforcement officers will be on duty, with s.w.a.t. teams and biochemical response units in place. >> protecting an event this large with this many different venues with this number of people coming requires a lot of coordination. >> reporter: president obama will take the oath again on martin luther king jr.'s birthday, this time with his hand on two bibles, one that king used and one that president l lincoln used. >> you're going to see a president that wants to work across party lines to get things done. i